Thirteen times since 1961, New Jersey voters have told their leaders they wholeheartedly support open-space preservation. They’ll have the opportunity to weigh in again in November, and we hope they’ll send Trenton the same unconditional message.

At issue is a referendum that would change the state Constitution to secure a long-term, stable and sustainable source of funding for New Jersey’s open-space program, rightly considered one of the most visionary in the nation.

Under the Green Acres and Blue Acres initiatives, the state buys land to assure clean water supplies, to create and maintain parks and fish and wildlife areas, and to protect flood-prone areas.

In this, the most densely populated of the 50 states, preserving what remains of our open spaces is not a luxury. It’s an imperative.

The N.J. Department of Environmental Protection recently released a draft report warning that although the aggressive Green Acres program has protected some 650,000 acres from developers’ bulldozers and cranes, at least that many acres are still needed to assure water quality, to provide parks and other recreational venues, and to keep agriculture thriving.

The problem: How to pay for those acres?

If approved, the proposed constitutional amendment will require that the 4 percent of the Corporation Business Tax currently dedicated to environmental programs be used mostly to fund open space programs. That share would increase to 6 percent of the corporation business tax after five years.

Advocates say the change could initially generate about $71 million annually, rising to $117 million when the higher figure kicks in. Supporters on both sides of the aisle believe the amendment will provide a steadier income source for open space than the 13 previous bond issues have.

Those short-term measures inevitably left funding gaps; the most recent $400 million bond issue, okayed by voters in 2009, ran dry last year.

The proposed constitutional amendment would help pay for cleaning up polluted sites that litter the state and for removing outdated underground tanks. It also would also help the Blue Acres initiative acquire land prone to flooding, and continue funding for watershed protection.

Most critically, the amendment would help stop New Jersey from becoming the first state to “build out” – a very real threat.

Amending the state Constitution is not something to be done on a whim. But when a solution so sensible exists to address a threat so eminent, we urge: Mark the ballot for Yes in November.